Dear, 

I am not able to build the modules.tar.gz from the
bitbake core-image-minimal. I am able to build the ramdisk.cpio.gz and dtb. 

Please suggest how can I build modules.tar.gz ?

In the local.conf( /AGL_TOP/koi/raspberrypi4/conf) do the following addition

DISTRO_FEATURES_append = " ram"
IMAGE_FSTYPES_append = " cpio.xz"
CORE_IMAGE_EXTRA_INSTALL += " kernel-modules"
MACHINE_EXTRA_RRECOMMENDS

/AGL_TOP/koi/raspberrypi4/
bitbake -k core-image-minimal